Prosecutors investigating claims of widespread tax evasion have raided the offices of HSBC's Swiss private arm in Geneva amid a growing row in Britain over coverage of the bank which has seen a high profile Daily Telegraph columnist resign in protest.

In a scathing editorial published on the Open Democracy website, he accused management of burying reports on the black hole in the HSBC accounts, which he infers was at the behest of the advertising department. “The Telegraph’s recent coverage of HSBC amounts to a form of fraud on its readers,” he said. “It has been placing what it perceives to be the interests of a major international bank above its duty to bring the news to Telegraph readers. There is only one word to describe this situation: terrible.”

In interviews with Channel 4 and BBC's Radio 4 Today, Oborne stepped up his criticism of his former employer's management, saying he believed the "vast majority" of the paper's newsroom had no confidence in its chief executive Murdoch MacLennan or in the paper's owners, the Barclay Brothers.

"As a journalist, it makes you feel sick," he told Today. "I do think that the Telegraph does have some explaining to do, they put out a statement yesterday that says my article was basically a tissue of lies. If that is so, they need to come and explain exactly what were the editorial guidelines being used that justified this.

Oborne said the Telegraph must now call an independent review into the relationship between advertising and editorial, and suggested the former editor Charles Moore or the current editor of the Spectator Fraser Nelson, should conduct it.

Referring to the Guardian's claim that HSBC had put its advertising "on pause", Oborne said there was a "pattern developing... that looks to an outsider like advertising is being used as a tool to suppress free speech".

A Telegraph spokesperson said on Tuesday: “Like any other business, we never comment on individual commercial relationships, but our policy is absolutely clear.

“We aim to provide all our commercial partners with a range of advertising solutions, but the distinction between advertising and our award-winning editorial operation has always been fundamental to our business. We utterly refute any allegation to the contrary. It is a matter of huge regret that Peter Oborne, for nearly five years a contributor to the Telegraph, should have launched such an astonishing and unfounded attack, full of inaccuracy and innuendo, on his own paper.”

"If they want to trash what I wrote yesterday, they need to come out and explain what the editorial procedure was that allocated six pars [paragraphs] at the bottom left of page 2 to the HSBC story," Oborne told the BBC.

Oborne has been widely praised across Fleet Street in this morning's papers, with some hinting that further departures from the Telegraph could be to come.

I'm hearing of yet another big name departure from the Telegraph is imminent. Not quite on the scale of Oborne, but near.

"If the Telegraph is wounded by Peter’s allegations it is also the case that HSBC’s already bruised reputation has taken another battering today," Massie wrote. "The bank is, as I say, free to spend its marketing budget as it sees fit but the idea it can think it reasonable to bully and threaten newspapers if they dare to run ‘unhelpful’ stories is another example of an over mighty corporation that evidently thinks the world deserves to be arranged in ways that comfort HSBC."